The present invention relates to ink jet recording materials and method for making the same. The material has a gel layer formed on a base material to improve the printing quality of ink of black pigment type.
Ink jet printers are fast developing in resent years. Meanwhile, the technologies for ink and recording materials are continuously improving. Generally, ink can be classified into two categories as dye type and pigment type. The manufacturing of recording material is to coat an ink-receptive layer on a base layer, such as paper. The ink-receptive layer will fast absorb ink droplets when the ink droplets are jetted from a print head to the recording material. Only when each ink droplet is even and fast absorbed, no spreading, feathering or penetration occur, the good quality of printing can be achieved. But due to the compatibility of a specific ink to its suitable recording materials, the ink and the ink-receptive layer of a recording material have to be well designed.
To determine if a recording material is suitable for an ink, an index of optical density of the material can be checked. The optical density is the reflection density of an ink jet image on the recording material. A higher optical density means a lower reflection, the ink is well absorbed on the material without cleavage or small holes, and a better print quality is obtained. On the contrary, a lower optical density means poor ink absorbency of the material, cleavages or holes occur in the ink dots, the print color is not true, and the print quality is poor.
Regarding to using pigment type ink, a recording material disclosed in U.S. Pat. No. 5,643,631 is made with an ink-receptive layer of precipitated calcium carbonate and a binder on a base layer. The ink-receptive layer will absorb the ink and prevent it from color mixing, feathering, unevenness or cleavages in order to obtain better print quality. The material according to 5,643,631 patent has been tested its optical density of image printed by an HP printer and tested on a reflection densitometer. The result is listed as in TABLE 1 in which four recording materials A, B, C and D are made of different ratios of precipitated calcium carbonate and a binder.
As shown in TABLE 1, the optical density of material according to 5,643,631 patent are in the range of 0.98 to 1.22 which are not quite high. That means the ink absorbency and drying speed are not good enough for achieving the high print quality demand today. Especially for high speed printing, when more ink drops jetted on the recording material in a short time, the material has to absorb and dry the ink drops quickly, and, most importantly, grab all the ink drops firmly without generating cleavages or holes. Therefore, for obtaining a better print quality, the optical density of a recording material has to be raised.
The object of the present invention is therefore to provide a recording material for using on an ink jet printer or ink jet modem which has a suitable higher optical density for improving print quality of ink of pigment type.
According to the present invention, an ink jet recording material has a gel layer formed on a base material to improve the optical density of the material and improve the printing quality of ink of pigment type. The method for forming the gel layer is to coat a first ink-receptive layer composed of high valance metallic halide, such as calcium chloride (CaCl2) or magnesium chloride (MgCl2), on the base layer, then a second ink-receptive layer composed of alginate, such as sodium alginate, potassium alginate or other compounds of alginic acid, on the first ink-receptive layer. The second and the first ink-receptive will react to form a gel layer during coating the second layer.
The objectives and advantages of the present invention will become apparent from a detailed description provided below, with reference to the accompanying drawings.